"show errors" when wrapped package does not compile properly

Hi!
We have some packages that were generated by Oracle Warehouse Builder.
The package header has a "valid" status, but the package body is
"invalid".
Using Enterprise Manager, I can't see the source code of the package
body. Seems like it is wrapped.
If I try to compile the package I get this:
SQL> alter package dwhstaging.map_b3000t_ei_a04_b3000t_002 compile;
Warning: Package altered with compilation errors.
SQL> show errors
No errors.
Is thee a way to find out what going wrong?
This is 9.2 on HP_UX 11i; Warehouse Builder 9.2
Thanks,
Helmut
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